Science of Biodiversity
WHY DO WE VALUE BIOLOGICAL DIVERSITY AND WHY IS BIODIVERSITY SO IMPORTANT FOR CLIMATE MITIGATION???
When you look at a commercial corn field, you see an ecosystem that has been modified for productivity. The corn no longer can protect itself; we must use chemicals to protect the corn. The corn no longer has enough nutrients or water in the soil to support the plant; we must add fertilizer and irrigate. This results in a production system that depends upon multiple fossil fuel subsidies in order to grow, and the costs of this albeit massive amount of production is large and growing. While we generate a lot of food in this process, we continue to mine the soil of its nutrients, we reduce the ability of the soil to hold carbon, and we pollute ground and stream water. Many benefits, but many costs that appear to be increasing faster than the benefits. The future demands that we find a better way, the answers are coming fast. We can find ways to enhance soil nutrient status and soil moisture and in doing so have the soils retain more carbon, thereby reducing greenhouse gases. While biodiversity is very important for many additional reasons across multiple community types, focusing on what biodiversity can do for agriculture is particularly relevant in our region.
While the relationship between the number of organisms in a community and the benefits provided by those organisms can take various forms, the generalized relationship is shown in the first figure.
The most common relationship seen in many communities shows that as species increase from a single species (i.e., the corn monoculture) to multiple species, benefits tend to increase quickly. Benefits continue to occur but decline in the rate of increase as the number of species increase. Finally we can ‘saturate’ a community where adding more species appears to have little or no effect on benefits. There’s still potential value in those ‘extra species’ however. During very dry years the drought adapted species can act to provide the ecosystem service, even though those species might not contribute in normal years. Redundancy is a good thing. Just ask anybody who runs a nuclear power plant.
Biodiversity in agricultural systems:
“Our results have implications for degraded agroecosystems, suggesting that increasing plant functional biodiversity may help restore their soil fertility. Creative applications of our findings to pastures, cover crops, and intercropping systems may provide greenhouse gas benefits from soil carbon storage and reduce the amounts of fertilizers needed for optimal yields.” (Furey and Tilman 2021)
There’s very solid evidence that planting landscapes that were formerly used for commercial agricultural purposes will increase soil carbon. And, as shown in the next figure, planting 16 species increases soil carbon substantially faster than planting just a single species.
Here’s some more data about that Minnesota experiment:
Individual points on the above graph show results from individual plots. It’s not until you get a fairly large sample that the trends and importance of plant diversity are observed. But also note that the average carbon gain in the soil per year of this experiment, which goes from a ‘old agricultural field to a planted grassland, is about 450 lb of carbon added per acre! In terms of greenhouse gas removed (carbon dioxide rather than just carbon), that’s 1650 lb of carbon dioxide per acre! If you had 10 acres, this would ZERO OUT your carbon footprint (and that’s the carbon you contribute to the atmosphere directly and indirectly from your entire lifestyle, not what you breath!). Plant a new species today! It will make you breath easier!
So, biodiversity is not the answer to add carbon in every plot or in every landowner’s yard, but on average and in general, biodiversity is a good thing for slurping carbon dioxide out of the atmosphere. This is one of ‘nature’s benefits’ (ecosystem services) that is in addition to increasing soil health, overall productivity, and provisioning services (both directly…we can eat some of these plants…and indirectly via support of pollinators.)
Read more here about a citizen soil health project that has vastly the improved soil health - and you can TOO!